Electronic shark-repelling cable installed in South Africa

South Africa has started testing a shark-repellent electronic cable in Cape Town to protect swimmers without harming the fish.

The technology uses a cable fixed to the seafloor featuring vertical 'risers' that support electrodes, which emit a low-frequency, low-power electronic field shown to repel sharks.

Sharks possess a sensory organ in their snout known known as the Ampullae of Lorenzini that allows them to find prey by detecting minute electrical impulses generated by their nervous systems, but larger electronic fields have been found to cause discomfort for the sharks and make them turn away.

The 100m cable now deployed at Glencairn Beach near Cape Town is based on a portable device called SharkShield invented by researchers at KwaZulu-Natal Sharks Board that generates an electromagnetic field to protect scuba divers and surfers.

If successful, the system could be an environmentally friendly alternative to the nylon shark nets used on the South African coastline for the past 50 years and which have been criticised for being occasionally lethal for marine life.

"Everybody is 100 per cent behind this project from the government to environmentalists, because this means we will have fewer sharks ending up dead from being trapped and tangled in the shark nets," said Paul Von Blerk, KwaZulu-Natal Sharks Board's technology specialist.

The bay, which will host the cable for a five-month pilot, was chosen because sharks appear there frequently during the summer months and clear waters in the area will make it easier for monitors to see whether the barrier does prove a deterrent.

The cable does not provide a physical barrier to sharks or other marine animals and researchers said the technology presents no risk to humans as the cable on the seabed will be covered and the electrodes will only produce a tingling sensation if touched.

The technology is backed by a study off the coast of South Africa, published in the journal PLOS One in 2013, that found attaching a SharkShield portable device to bait significantly reduced the number of approaches by sharks and greatly increased the amount of time it took for them to eventually strike, though it didn’t prevent the sharks from eventually taking the bait.